Chlorine-alkali electrolysis

Transcription

1 Chlorine-alkali electrolysis Inline analytical technology for: brine purification electrolysis chlorine gas drying NaOH concentration hydrochloric acid production

2 Increasing q Robust, acc With high LiquiSonic

3 LiquiSonic 3 uality, saving resources: LiquiSonic. -value, innovative sensor technology. urate, user-friendly. LiquiSonic is an inline analytical system for determining the concentration in liquids directly in the production process. The analyzer is also used for phase separation and reaction monitoring. Sensor installation within the product stream means an extremely fast measurement that responds immediately to process changes. User benefits include: optimal plant control through online and real-time information about process states maximized process efficiency increased product quality reduced lab costs immediate detection of process changes energy and material savings instant warning of irruptions in the process water or process liquid repeatable measuring results LiquiSonic s state-of-the-art digital signal processing technology guarantees highly accurate, fail-safe measuring of absolute sonic velocities and liquid concentrations. Integrated temperature detection, sophisticated sensor design, and know-how from SensoTech s extensive measurement history in numerous applications promises users a highly reliable, long-lived system. Advantages of the measuring method are: absolute sonic velocity as a well-defined and retraceable physical quantity independence from conductivity, color or optical transparency of the process liquid installation directly into pipes, tanks or vessels robust, all-metal, gasket-free sensor design with no moving parts corrosion-resistant by using special material maintenance-free use in temperatures up to 200 C (392 F) accurate, drift-free measurements stable measurements even amid gas bubbles controller connection capacity reaching up to four sensors data transmission via fieldbus (Profibus DP, Modbus), analog outputs, serial interface or Ethernet

4 Inline process analysis

5 Contents 5 Contents 1 Process Introduction Dissolving station and brine purification Electrolysis Preparation of end products Caustic soda concentration Chlorine gas drying Hydrochloric acid production 9 2 LiquiSonic system Measuring principle Sensor Controller Technical specifications 13

6 6 1 Process Photo Vinnolit

7 H SO 2 4 Cl (H O) 2 2 Process Introduction The chlorine-alkali electrolysis is an important procedure in the chemical industry. Here the products chlorine, hydrogen, hydrochloric acid and caustic soda are generated from sodium chloride. There are three manufacturing methods: the diaphragm, the membrane and the amalgam process. The LiquiSonic analyzer provides an advantageous utilization in the varied process steps of the three methods. Foremost, the customer gains the advantages of a reduction in raw material and energy consumption, as well as an increase in the yield. The diagram below shows the typical processes and LiquiSonic applications in the chlorine-alkali electrolysis, which is illustrated in a sample diaphragm method. NaCl 1 H O 2 precipitant H SO Cl2 (< 30 ppm H O) 2 dissolving vessel chlorine gas drying pressure filter NaCl H O 2 Cl 2 2 H 2 catholyte (NaOH, NaCl) HCl 4 Cl 2 Cl - Na + Cl - OH - H 2 OH - H 2 O 15 + steam separation H 2 Burner with falling film absorber + - electrolyser 6 NaOH Measuring point Installation Measuring task 1, 2 pipe 3 pipe monitoring of the delivered brine to the agreed target concentration, monitoring of the dissolving station to the maximum salt saturation determination of the sulphuric acid concentration during the chlorine gas drying to avoid too strong dilution 4 pipe determination of the required final concentration of HCl 5 pipe maximizing of the effectiveness degree of the electrolyzer, through the determination of the catholyte concentration 6 pipe determination of the required final concentration of NaOH LiquiSonic measuring points in the processes of the diaphragm method of the chlorine-alkali electrolysis

8 8 1.2 Dissolving station and brine purification The raw material sodium chloride (NaCl) is gained by either the vaporizing of sea water, mechanical or solution mining of salt deposits. The raw brine contains contaminants and calcium or magnesium salts, that clog the fine pores of the diaphragm or the membrane during the electrolysis and can thereby visibly reduce their lifespan. It is for this purpose that the contaminants are precipitated in the agitation plant containers (dissolving vessels), through the addition of caustic soda. After the precipitating, the contaminants are separated with the aid of a pressure filter. The purity of the brine concentration is especially important for the subsequent electrolysis. The LiquiSonic analyzer offers the ability to determine a very precise brine concentration at any time. The installation takes place in the dissolving station in the case of mechanically mined salts, or at the brine suppliers transfer point in the case of cavern mining. Your advantage: avoiding of quality failures during the brine purification extending of the membrane s lifespan incoming goods inspection (in cavern mining) reduction in water and/or steam consumption (during the salt dissolving) reduction in electrical energy consumption 1.3 Electrolysis With the help of electrical power, the salt (NaCl) is broken down into chlorine (Cl 2 ), caustic soda (NaOH) and hydrogen (H 2 ). For this purpose, two methods are primarily utilized: the diaphragm and the membrane method. With both methods, the same electrochemical reaction occurs: The NaCl flows into the anode chamber of the cell, where the CI 2 separates as chlorine gas. Subsequently, the solution reaches the cathode chamber, where H 2 and NaOH are formed. The deciding difference in both methods, lies in the technical execution of the anode and cathode separation, which is crucial for the purity and concentration of generated caustic soda. The membrane and the diaphragm constitute a high cost factor within both methods. The LiquiSonic analyzer is utilized for a precise determination of the catholyte concentration, in order to identify possible electrolyzer inefficiencies and to counteract them. This way, an optimum membrane lifespan can be achieved. Depending on which method is utilized, the catholyte involves either a NaOH-solution (membrane method) or a NaOH-NaCl-solution (diaphragm method). The concentration measurement of the 3-component mixture is accomplished with the use of a Liquisonic 40 analyzer, whereby the ultrasonic sensor is combined with a conductivity probe. Your advantage: maximizing of the electrolyzer s effectiveness degree, through the continuous concentration measurement directly in the process energy saving and consumption optimizing reduction in labor intensive comparison analyses extending of the membrane s lifespan 1.4 Preparation of end products Caustic soda concentration The market ready caustic soda (NaOH) typically has a concentration between 45 wt% and 50 wt%. Due to the fact that NaOH gained from electrolyzer cells only yields a concentration range between 12 wt% and 33 wt%, it is concentrated in cascade evaporators. If next to NaOH the solution contains NaCl (diaphragm method), the excess salt in the caustic soda precipitates in a crystal form during the evaporation. This way, the NaOH-concentration is elevated to 45 wt% and 50 wt%. The LiquiSonic analyzer continuously determines the concentration of caustic soda at any time after the evaporator. A subsequent dilution of the caustic soda to a customer specific product concentration, can also be monitored. Your advantage: continuous concentration monitoring of the caustic soda reduction in the energy costs during the evaporation

9 Process Chlorine gas drying The chlorine gas must be freed of its water content before it is further processed, due to the fact that its corrosiveness elevates at a moisture content of over 30 ppm. For the drying, the chlorine gas is routed into the absorption towers, where the water content in the chlorine gas is absorbed with highly concentrated sulphuric acid (80-99 wt% H 2 SO 4 ). The effectiveness of this drying process significantly influences the productivity and quality of the gas. This is why a reliable measurement of the H 2 SO 4 - concentration is especially important. The LiquiSonic analyzer offers a continuous and safe monitoring of the H 2 SO 4 -concentration, in opposition to conductivity and density measurement. Your advantage: elimination of labor intensive sampling continuous monitoring of H 2 SO 4 -concentration clear concentration determination signal between 80 wt% and 100 wt% H 2 SO 4 ensuring the desired Cl 2 dryness to avoid corrosions in the system Hydrochloric acid production The chlorine gas that is generated on the anode of the electrolyzer and the added hydrogen, form the base materials for the synthesis of hydrochloric acid. For this, both gases are fed into a burner and there they react to form hydrogen chloride. Subsequently, the formed HCI-gas streams from the burning chamber into the integrated isothermic falling-film-absorber. Here, the gas is absorbed with the help of water or diluted acid, whereby concentrated hydrochloric acid (37 wt% HCI) is formed. Using the LiquiSonic analyzer, a continuous monitoring of the hydrochloric acid concentration is possible. This affords the ability to recognize deviations from the target concentration and to react accordingly. Your advantage: continuous concentration monitoring of hydrochloric acid (20-40 wt% HCl) ensuring of an extremely precise target concentration Advantage of sonic velocity as compared to conductivity and density density [g/l] sonic velocity [m/s] no clear signal conductivity [ms/cm] no clear signal concentration [wt%] sonic velocity conductivity density

10 10 2 LiquiSonic system

11 LiquiSonic system LiquiSonic sensing is available in three systems: LiquiSonic 20, LiquiSonic 30 and LiquiSonic 40. LiquiSonic 30 is a highly efficient device that includes one controller with connection up to four sensors that can be installed in different locations. 2.1 Measuring principle The LiquiSonic ultrasonic analyzer can determine liquid parameters such as concentration or density, as well as being useful for phase separation and reaction monitoring. The measuring principle is based on the determination of sonic velocity in liquids. The sensor distance (d) between the sonic transmitter and receiver is known, so it is possible to determine sonic velocity (v) simply by clocking the travel time (t) of the sonic signal (v = d / t). Since sonic velocity depends on substance concentration, they form a direct relationship to compute and control concentration levels. Controller with connection of maximum four sensors LiquiSonic 20 is an economical single-channel solution. The ultrasonic measuring method is independent of a liquid s optical transparency and features high accuracy, repeatability and reliability. Complementing the sonic velocity measurement, the LiquiSonic analyzer includes a fast, accurate temperature measurement for temperature compensation offering great benefits for many applications where conventional measuring methods are limited. LiquiSonic 40 enables the simultaneous determination of two concentrations in one liquid mixture by tracking a second physical quantity in combination with sonic velocity. In chlorine-alkali processes, the LiquiSonic 40 system includes a conductivity probe as second physical value. conductivity sensor ma 24 VDC controller Measuring principle of sonic velocity Halar coated sonic velocity sensor connection process control system LiquiSonic bus 24 VDC LiquiSonic 40 application 11

12 Sensor The LiquiSonic sensor continuously senses both concentration and temperature in pre-defined ranges for updating all process-related information every second. The liquid-wetted parts of the sensor are made of stainless steel or corrosion-resistant material such as Hastelloy C-2000, Halar or PFA. The rugged, completely enclosed design requires no gaskets or window, making it totally maintenance-free. Additional sensor features such as flow / stop or full / empty pipe monitoring greatly advance process control. Special high-power technology stabilizes measuring results, even when facing gas-bubble accumulations or large-scale signal attenuation through the process flow. 2.3 Controller The controller processes and displays the measuring results. The operation via the high resolution touch screen is easy and intuitive. Secure network integration including web server allow operating the controller alternatively via browser with a PC or tablet. The data can be transmitted in several defined analog-digital forms or through different fieldbus interfaces to communicate with process control systems or computers. It is possible to create user-configured thresholds to regulate the process to avoid undesirable process states, including acid runaway. The controller features an integrated data logger which can store up to 2 GB of process information with up to 32 (optional 99) data sets for different process liquids. For processing on the PC, the data can be transferred via network or USB port. In addition, the controller enables creating easily process reports for documentation purposes. The event log records states and configurations such as manual product switches, changes to date and time, alarm messages or system states. Accessories include: fieldbus UMTS router network integration & web server rack-mounted housing (anodized aluminium) wall-mounted housing (plastic or stainless steel) Immersion sensor Controller integrated in the wall-mount plastic housing

13 LiquiSonic system Technical specifications controller type controller 20 controller 30 controller 40 sensor type immersion sensor sensor material H 2 SO 4 : Hastelloy C-2000 NaOH: Stainless Steel HCl: Halar NaCl: Hastelloy C-2000/Titan NaOH/NaCl: Hastelloy C-2000/Titan & PFA coated conductivity probe sensor length customized minimum process temperature -20 C (-5 F) maximum process temperature 120 C (250 F) optional 200 C (390 F) maximum process pressure 250 bar (3626 psi) process fitting DIN ANSI others on request interface analog outputs: 4 x 4-20 ma Modbus RTU Profibus DP digital outputs: 6 x electronical relays concentration range H 2 SO 4 : wt% NaOH before evaporator: wt% NaOH after evaporator: wt% HCl: wt% NaCl: wt% NaOH/NaCl: 0-15 wt% NaOH and 0-25 wt% NaCl Ex approval ATEX IECEx FM protection degree IP65 IP67 IP68 NEMA 4X NEMA 6P ambient temperature range -20 C to 60 C (-5 F to 140 F) accuracy sonic velocity: up to ± 0.1 m/s concentration: up to ± 0.05 wt%

14 Setting the stan With passion All based on ab SensoTech

15 SensoTech 15 dards for process analysis., that creates new solutions. solute spirit of development. SensoTech is a provider of systems for the analysis and optimization of process liquids. Since our establishment in 1990, we have developed into a leading supplier of process analyzers for the inline measurement of liquid concentration and density. Our analytical systems set benchmarks that are used globally. Manufactured in Germany, the main principle of our innovative systems is to measure ultrasonic velocity and density in continuous processes. We have perfected this method into an extremely precise and remarkably user-friendly sensor technology. Beyond the measurement of concentration and density, typical applications include phase interface detection or the monitoring of complex reactions such as polymerization and crystallization. It is our goal to ensure that you maximize the potential of your manufacturing facilities at all times. SensoTech systems provide highly accurate and repeatable measuring results even under difficult process conditions. Inline analysis eliminates safety-critical manual sampling, offering real-time input to your automated system. Multi-parameter adjustment with high-performance configuration tools helps you react quickly and easily to process fluctuations. We provide excellent and proven technology to help improve your production processes, and we take a sophisticated and often novel approach to finding solutions. In your industry, for your applications no matter how specific the requirements are. When it comes to process analysis, we set the standards. Our LiquiSonic measuring and analysis systems ensure optimal product quality and maximum plant safety. Thanks to their enhancing of efficient use of resources they also help to reduce costs and are deployed in a wide variety of industries such as chemical and pharmaceutical, steel, food technology, machinery and plant engineering, car manufacturing and more.

16 SensoTech GmbH Steinfeldstr Magdeburg-Barleben Germany T F info@sensotech.com SensoTech Inc Hamburg Tpk. Wayne, NJ USA LSM231_01_04_R 06/2018 Photo ThyssenKrupp SensoTech (Shanghai) Co., Ltd. 申铄科技 ( 上海 ) 有限公司 No. 889, Yishan Road, Xuhui District 上海市徐汇区宜山路 889 号 Shanghai 上海 China 中國 电话 传真 sales-china@sensotech.com T F sales-usa@sensotech.com